The present invention relates to a method for the preparation of triorganochlorosilane.
Triorganochlorosilane is used as an intermediate for silicone products such as silicone rubbers, silicone oils, and so forth. Triorganochlorosilane is also used as a silylating agent for the protection of functional groups on precursors during the synthesis of organic chemicals such as pharmaceuticals, agrichemicals, dyes, and so forth.
Methods for the preparation of triorganochlorosilane from triorganohydrosilane include the reaction of triorganohydrosilane with chlorine.
Specifically, triorganochlorosilane carrying a non-methyl substituent on the silicon is generally synthesized by first reacting SiH-containing diorganochlorosilane with an organometallic compound (e.g., Grignard reagent, etc.) to yield the triorganohydrosilane and then reacting the triorganohydrosilane with chlorine to afford the triorganochlorosilane.
There has recently been recognition of the extreme usefulness of highly sterically hindered silylating agents with a better protective group inertness than trimethylchlorosilane, for example, trialkylchlorosilanes such as tert-butyldimethylchlorosilane, triisopropylchlorosilane, and triethylchlorosilane. As a result, such silylating agents are being used with increasing frequency. As explained above, silylating agents carrying such substitutents can be synthesized starting from a dialkylhydrochlorosilane. The necessary alkyl group is first introduced onto the silicon atom, and the Si-H group on the resulting trialkylhydrosilane is then chlorinated with chlorine. A drawback to this method is the inconvenience associated with the handling of chlorine, and sulfuryl chloride (SO.sub.2 Cl.sub.2), a well-known chlorine equivalent, is therefore used in some cases in place of chlorine.
However, the chlorine and sulfuryl chloride (chlorine equivalent) used in this prior-art method exercise a poor reaction selectivity. This results in the synthesis of both trialkylchlorosilane (chlorination of the silicon-hydrogen bond) and chloroalkyl-containing silane by-products (chlorination of carbon-hydrogen bonds on the alkyl group), and the yield of the desired trialkylchlorosilane is therefore diminished. In addition, these chloroalkylsilane by-products do not currently have any value insofar as practical applications are concerned, and their disposal as industrial wastes is problematic from the standpoint of environmental preservation.
The present invention was developed as the result of extensive investigations by the inventor in order to solve the problem described above. The preparative method in accordance with the present invention makes possible the high-yield synthesis of triorganochlorosilane without the generation of by-products.